The role of chloroplast NAD(P)H dehydrogenase in protection of tobacco plant against heat stress

The environmental temperature is one of the mainfactors affecting plant growth and development. Insummer, plants are frequently influenced by hightemperature. In recent years, global temperature wasremarkably elevated accompanied with the climaticchanges,…     

超声激活血卟啉对S180 肿瘤细胞表面EGFR 表达量的影响

目的：探讨超声激活血卟啉处理S180肿瘤细胞后膜表面EGFR表达量的变化。方法：将腹水瘤细胞随机分为四组,U组和UH组细胞分别于频率1．8MHz、2．0W／cm^2的超声装置中照射3min,并分别在1h3h5h后取材,应用免疫组化方法在光镜下观察EGFR的表达情况。结果：1h、3h取材,U组和UH组平均光密度值明显低于Cr组和H组,UH组最低。而5h取材时,UH组平均光密度值显著下降,其它组基本无变化。结论：提示在高频低强度处理下,随着时间的延长,超声激活HpD对EGFR的抑制作用增加,显示可能是基因调控使EGFR表达下调,从而使肿瘤细胞增殖减慢。     

家蚕细胞色素P450基因Bmcyp6u1的克隆、序列分析与表达谱

细胞色素P450第6亚家族基因为昆虫所特有,与抗性相关。为了检测家蚕Bombyx mori cyp6u1基因是否与耐氟性相关,首先克隆了cyp6u1基因。采用生物信息学方法获得与黑腹果蝇Drosophila melanogaster cyp6u1基因同源的家蚕B. mori cyp6u1基因序列, 预测该序列的开放阅读框（ORF）为1 476 bp, 编码491个氨基酸, 推定的蛋白质分子质量为56.15 kD, 等电点为9.23。以家蚕5龄第3天幼虫精巢cDNA为模板, 设计特异引物PCR扩增出一条约1 500 bp的条带, 大小与家蚕cyp6u1序列的ORF预测值接近, 命名为Bmcyp6u1基因（GenBank登录号：HM130560）。同源性分析表明, Bmcyp6u1基因与蜜蜂Apis mellifera的同源基因cyp6AS13的相似性为56%, 与拟南芥Arabidopsis thaliana的cyp72A82的相似性为48%, 与人Homo sapiens的cyp3A7基因的相似性为50%。芯片数据分析表明, Bmcyp6u1基因在家蚕5龄第3天幼虫各组织表达量很低, 只在精巢组织(5龄第3天)稍有表达, 推测该基因具有组织特异性。     

Changes in apolar metabolites during in vitro organogenesis of Pancratium maritimum

Calli, shoot-clumps and regenerated plants were initiated from young fruits of Pancratium maritimum L. Their genetic stability was monitored by flow cytometry before chemical studies. Apolar metabolites (alkaloids extracted at pH > 7, free fatty acids and fatty alcohols, sterols etc.) were qualitatively and quantitatively analyzed by GC–MS. The results clearly demonstrated that alkaloid synthesis in P. maritimum is closely related with tissue differentiation. The highest amounts of alkaloids and presence of homolycorine and tazettine type compounds (end products of the biosynthetic pathway of the Amaryllidaceae alkaloids) were found in highly differentiated tissues. Galanthamine accumulated in the leaves of plantlets. The amount of hordenine, a protoalkaloid, is related with the ability of tissues to synthesize alkaloids. Saturated fatty acids were found in considerably higher levels in undifferentiated callus cultures and partially differentiated shoot-clumps than in regenerated plants. Mono- and dienoic fatty acids were found at higher levels in non-photosynthesizing tissues – calli, and in vitro and intact bulbs, while α-linolenic acid (trienoic acid) was found in higher amounts in the photosynthesizing leaves of shoot-clumps and regenerated plants than in bulbs and calli. Fatty alcohols were found mainly in leaves, while sterols tended to accumulate in photosynthesizing and undifferentiated tissues.     

EGF and its related growth factors mediate sodium transport in mpkCCDc14 cells via ErbB2 (neu/HER‐2) receptor

Amiloride‐sensitive sodium entry, via the epithelial sodium channel (ENaC), is the rate‐limiting step for Na⁺ absorption. Epidermal growth factor (EGF) is involved in the regulation of Na⁺ transport and ENaC activity. However it is still controversial exactly how EGF regulates ENaC and Na⁺ absorption. The aim of the present study was to characterize the EGF regulation of Na⁺ transport in cultured mouse renal collecting duct principal mpkCCD_c14 cells, a highly differentiated cell line which retains many characteristics of the cortical collecting duct (CCD). EGF dose dependently regulates basal transepithelial Na⁺ transport in two phases: an acute phase (<4 h) and a chronic phase (>8 h). Similar effects were observed with TGF‐α, HB‐EGF, and amphiregulin which also belong to the EGF‐related peptide growth factor family. Inhibition of MEK1/2 by PD98059 or U0126 increased acute effects and disrupted chronic effects of EGF on Na⁺ reabsorption. Inhibition of PI3‐kinase with LY294002 abolished acute effect of EGF. As assessed by Western blotting, ErbB2 is the most predominant member of the ErbB family detected in mpkCCD_c14 cells. Immunohistochemistry analysis revealed localization of ErbB2 in the CCD in Sprague–Dawley rat kidneys. Both acute and long‐term effects of EGF were abolished when cells were treated with tyrphostin AG‐825 and ErbB2 inhibitor II, chemically dissimilar selective inhibitors of the ErbB2 receptor. Thus, we conclude that EGF and its related growth factors are important for maintaining transepithelial Na⁺ transport and that EGF biphasically modulates sodium transport in mpkCCD_c14 cells via the ErbB2 receptor. J. Cell. Physiol. 223: 252–259, 2010. © 2009 Wiley‐Liss, Inc.     

How initiation factors tune the rate of initiation of protein synthesis in bacteria

The kinetics of initiator transfer RNA (tRNA) interaction with the messenger RNA (mRNA)-programmed 30S subunit and the rate of 50S subunit docking to the 30S preinitiation complex were measured for different combinations of initiation factors in a cell-free Escherichia coli system for protein synthesis with components of high purity. The major results are summarized by a Michaelis-Menten scheme for initiation. All three initiation factors are required for maximal efficiency (kcat/KM) of initiation and for maximal in vivo rate of initiation at normal concentration of initiator tRNA. Spontaneous release of IF3 from the 30S preinitiation complex is required for subunit docking. The presence of initiator tRNA on the 30S subunit greatly increases the rate of 70S ribosome formation by increasing the rate of IF3 dissociation from the 30S subunit and the rate of 50S subunit docking to the IF3-free 30S preinitiation complex. The reasons why IF1 and IF3 are essential in E. coli are discussed in the light of the present observations.     

Hormonal stimulation of maturation and ovulation of oocytes in Zebrasoma scopas (Acanthuridae)

The experiments were carried out on hormonal stimulation of oocyte maturation in Zebrasoma scopas from the South China Sea, Vietnam. Three variants of surfagon injections were studied: 1—double injections (5 + 20 μg/kg of fish body weight); 2—double injections (2 + 8 μg/kg); and 3—single injections (20 μg/kg). The time interval between two injections comprised 15–24 h. Ovulation of oocytes in variants 1 and 2 was observed in most (67%) females 33–47 h after the first injection. The increase of the time interval between injections I and II was followed by the decrease of the interval between injection II and ovulation. In variant 3, oocytes ripened but ovulation was absent. The oocytes possessed with the competence for maturation are always present in the ovaries because of a continuous type of oogenesis. The morphological changes in oocytes in the process of maturation were observed. Ovulated oocytes could be stored in the ovary cavity no more than 4 h; the number of embryos with normal cleavage decreased during this time from 90 to 53%.     

Influence of emotional stimuli on behavior and respiration of rabbits with various locomotor activity in the "open field"

Different behavioral reactivity of rabbit groups differentiated by locomotor activity in the "open field" was revealed during exposure to emotional stimuli (rustle, loud sound, pressuring on back of the neck, vibroacoustic tactile stimulation of an ear). In passive rabbits, the active locomotor reactions were induced harder and freezing was obtained easier than in active animals. During exposure to sound stimuli, passive rabbits increased their locomotion more rarely than active animals, pressing on back of the neck produced longer freezing, a threshold of defensive ear shaking in response to a vibroacoustic stimulus in passive animals was highest. Training to mild immobilization increased the threshold of defensive responses in active rabbits and animals of the intermediate type. Changes in respiratory parameters were correlated with behavioral reactions to emotional stimuli. The duration of exhalation and respiratory cycle increased during freezing and increased during enhanced locomotion. The duration of inhalation decreased in response to emotional stimuli irrespective of a behavioral reaction. The respiratory reactions to emotional stimuli differed in rabbits of different groups. The respiratory rate more frequently changed in passive rabbits than in animals of other groups. Passive animals reacted mainly by exhalation, active rabbits and animals from the intermediate group predominantly responded by inhalation.